Catalytic bond forming reactions promoted by amidinate, guanidinate and phosphaguanidinate compounds of magnesium.

The synthesis and catalytic properties of a series of magnesium compounds consisting of monoanionic, N,N'-chelating ligands (N∩N = amidinates, guanidinates, phosphaguanidinates) is reported. The compounds were synthesized by (i) insertion of a carbodiimide into an existing Mg-C or Mg-N bond, or (ii) protonolysis of an organomagnesium compound by a neutral pre-ligand. Structural analyses of mono- or bis-(chelate) compounds with general formula Mg(N∩N)X(L)n and Mg(N∩N)2(L)n (X = halide, aryloxide, amide; L = Et2O, THF; n = 0, 1 or 2) have been performed and the influence that the ligand substituent patterns have on the solid-state structures has been probed. Selected examples of the compounds were tested as (pre)catalysts for the polymerization of lactide, the dimerization of aldehydes and the hydroacetylenation of carbodiimides.

Synthetic and catalytic intermediates in a magnesium promoted Tishchenko reaction.

Magnesium-aryloxide and -amide compounds supported by amidinate ligands are accessible in two-steps from a suitable Grignard reagent. Both species are active for the dimerization of benzaldehyde. The slower initiation by the aryloxide was exploited in the isolation of a bis-mesitylaldehyde adduct.